This invention pertains to fasteners. More particularly, the invention pertains to a nail with a shank having a plurality of spiral formed deformations configured to increase the holding power of the nail.
Round nails, that is, nails having cylindrical shanks, have been produced for hundreds of years. These are the easiest type of nail to manufacture, because of their symmetrical shape. Moreover, round nails exhibit relatively predictable, uniform properties, such as holding power, when driven into wood.
Holding power, or withdrawal strength, refers to the nail's resistance to an axial force (a load parallel to the nail shank). This includes the nail's resistance to withdrawing from the substrate into which it is driven.
Altering the shape of a nail shank to increase holding power is known. For example, ring shank nails are known, which have peripheral rings formed in the shank. The rings can extend from the head to the driving end or tip of the nail.
Other fasteners have grooves formed longitudinally along the shank. The shape and number of the grooves can vary and can include “star” or other shapes.
Still another nail, disclosed in Lat, U.S. Pat. No. 5,741,104, includes annular rings and a circumferential array of helical grooves that may be deeper or shallower than the annular rings.
While all of these alterations to the shape of the nail increase the holding power of the nail, there is always the potential for pull-out of the nails from the substrate.
Accordingly, inasmuch as there will always be the possibility that a nail will pull out unless the holding power is as great as the inherent strength of the substrate material (e.g., the lumber into which the nail is driven), there is a need for a nail having increased holding power. Desirably, such a nail is fabricated without the need for additional material (in the nail) over that of a standard nail of the same size, and without affecting the other characteristics (e.g., shear strength, hardness) of the nail.